Right way to use generics for cellular automatons?

Question

Hi,
i've got a question about using generic types in combination with subclassing (which should be used in a cellular automaton),
In fact there are only 3 classes that are necessary to understand my problem:
- Cell (abstract)
- CellularAutomaton
- SubclassedCell (extends Cell)
These classeses work as follows:
A cellular automaton holds some cell's with respect to the order they were added. The cell itself holds some properties and the most important function in this small "framework". This function is "performCellAction(CellularAutomaton ca)". It retrieves the "neighbor" cells from the given parameter and calculates a new state using these neighbors.
The way i implemented this using generics is:
public class CellularAutomaton<T extends Cell>{
  private List<T> cells;
  public T getLeftNeighbor(T cell) { ... } // gets the left neighbor of the given cell
  public T getRightNeighbor(T cell) { ... } // gets the left neighbor of the given cell
public abstract class Cell [
  public void performCellAction(CellularAutomaton<? extends Cell> ca) {}
public class SubclassedCell extends Cell {
  private String str;
  public void performCellAction(CellularAutomaton<? extends Cell> ca) {
    Cell left = ca.getLeftNeighbor();
    // PROBLEM:
    // How to call left.getStr() here???
    // How can i be sure that ca contains objects of class subclassedCell (or objects of subclasses of subclassedCell) ... and not objects of class cell or another subclasses cell
  public String getStr() {}
}In fact i found "something like a solution", which looks like this:
public class CellularAutomaton<T extends Cell>{
  private List<T> cells;
  public T getLeftNeighbor(T cell) { ... } // gets the left neighbor of the given cell
  public T getRightNeighbor(T cell) { ... } // gets the left neighbor of the given cell
  public void computer() {
    for (T cell: cells) {
      // compiler warning here!!
      cell.performCellAction(this);
public abstract class Cell<T extends Cell<?>> [
  public void performCellAction(CellularAutomaton<T> ca) {}
public class SubclassedCell extends Cell<SubclassedCell> {
  private String str;
  performCellAction(CellularAutomaton<SubclassedCell> ca) {
    SubclassedCell left = ca.getLeftNeighbor();
    left.getStr(); // works here
  public String getStr() {}
}However, even in this "working" solution i get a compiler warning at the method CellularAutomaton->computer():
The warning is Type safety: The method performCellAction(CellularAutomaton) belongs to the raw type Cell. References to generic type Cell<T> should be parametrized and Cell<T extends Cell<?>> also looks very uncommon to me.
Is there a betted way to achieve the goal to access left.getStr() in the performCellAction of the subclassed cell??
Regards,
Niko

Answer 1

I thought of that myself, but if i do this, i get the following error:
The method performCellAction(CellularAutomaton<capture#1-of ?>) in the type Cell<capture#1-of ?> is not applicable for the arguments (CellularAutomaton<T>)